FR2642480A1 - METHOD AND DEVICE FOR REGULATING THE OPERATING POINT OF A FAN MOUNTED ON AN AGRICULTURAL APPARATUS - Google Patents

Abstract

The invention relates to a method and a device for the automatic regulation of the operating point of a fan used in an agricultural device, the operation of which requires at least one source of pressure different from atmospheric pressure, between a minimum threshold and a minimum. maximum pressure threshold downstream of the fan and / or a minimum threshold and a maximum depression threshold upstream of said fan, for a flow rate of air absorbed by the fan between a first and a second terminal. According to the invention, the method consists in placing the upstream side of the fan in communication with the atmosphere so that the pressure downstream of the fan does not fall below said minimum pressure threshold and in placing the downstream side of the fan in communication. with the atmosphere so that the upstream depression does not fall below said minimum depression threshold. According to the invention, the device comprises a first calibrated valve 21, placed in the upstream part of the fan and a second calibrated valve 34, placed in the downstream part of the fan. Application to agriculture.

Description

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  The present invention relates to a method and a device for the automatic control of the operating point of a fan used in an agricultural apparatus whose operation requires at least one pressure source different from the atmospheric pressure. Some precision planter distributors are known to work with a vacuum. For example, patent EP-00 46709 discloses a vacuum pump for a precision seed drill comprising a rotary distribution disk provided with a circular file of perforations, a housing whose interior is divided by the disc into two contiguous enclosures one of which serves as a seed tank and the other of which extends over part of the trajectory

  perforations of the disc, constitutes a vacuum chamber.

  Other planter distributors operate at the same time thanks to a source of depression and a source of pressure. In particular, patent EP-00 37775 discloses a pneumatic ejector seeder intended in particular for sowing light seeds such as vegetable seeds, the seeder being of the type which comprises a distributor member for transporting seeds, means for releasing those -this

  said member in a drop zone, and an ejection device.

  The dispensing member comprises a perforated disk intended to rotate in front of a suction chamber placed on a first side of the disk and interrupted in the drop zone, the suction chamber being connected to a source of depression. The ejection device comprises an ejection venturi oriented towards the ground, attached to the other side of the perforated disk and having a convergent, connected to a source of compressed fluid, a neck having an inlet port of the seeds transported and held by the disk, and a divergent, the orifice formed in the neck or close to it being in or near the release zone, the neck of the venturi being further disposed relative to the suction chamber so that, when the seeds are released by the perforated disk, they are already substantially in the venturi neck or downstream of this neck. Also known are agricultural spreading devices, also called spreaders, which are intended for forced spraying of seed products or granules for the treatment of soils, 2 - such as fertilizers, herbicides, insecticides, and the like. which can also be used to sow seeds of small size, in a so-called "on the fly" sowing mode. Such apparatuses include means for speeding up and projecting the granular products which are supported by a chassis and fed with granular products from at least one hopper, as well as distribution means. The speed-up means are for example connected to a source of compressed fluid which makes it possible to communicate to the products a speed which ensures their projection towards the distribution means. These are generally constituted by a bundle of tubes of progressively decreasing lengths. These tubes guide and transport the

products down to the ground.

  In agricultural apparatus requiring only a source of pressure different from the atmospheric pressure, a vacuum source for, in particular, precision seed drills incorporating a dispenser conforming to patent EP-00 46709, or a source of pressure for, in particular, pneumatic spreading devices, this source can be generated

by a fan.

  However, an agricultural appliance may require two sources of pressure different from the atmospheric pressure, and in particular a source of depression and a source of pressure. This is the case for a pneumatic ejector seeder as described in patent EP-00 37775 or for an agricultural apparatus incorporating both a vacuum seeder and a pneumatic spreader. In this case, the sources of pressure and depression are usually

  generated by two or three fans.

  It is understood that the mounting of two or three fans on a

  device is relatively complex and expensive.

  If one wishes to use only a single fan to generate both a source of pressure and a source of depression,

  then pose problems regulating this fan.

  Indeed, each fan has operating characteristics such that for a flow of air absorbed by the fan, the total pressure of the fan, that is to say the sum of the absolute values of the upstream depression (or at the inlet) of the fan and the pressure downstream (or at the outlet) of the fan,

is imposed and constant.

  - 3 - However, the proper functioning of an agricultural machine, using both a source of pressure and a source of depression, imposes a

  minimum threshold of pressure and a minimum threshold of depression.

  It should also be noted that these minimum pressure and vacuum thresholds must not vary according to the use of the agricultural machine, although, for example, for an apparatus comprising both a seed drill using a disk dispenser with vacuum and a spreader, the number of discs, the structure of the discs and the depression applied to them vary according to, in particular, the average diameter of the seeds to be sown and the number of rows to be sown. In addition, the pressure of the compressed fluid used by the spreader must not be lower than a minimum threshold whatever the nature of the

  products to be distributed and the number of rows concerned.

  This functioning must therefore be ensured by a system of

regulation.

  It has been envisaged a control system by static shutters, occupying adjustable positions, and for fixing, for given operating conditions of the drill, the sections of the air ducts upstream and downstream of the fan. These static flaps could be operated manually by the user, with tables and graduations on the flaps, which requires a relatively long handling. They could also be enslaved to a logic of control so as to make their

automatic operation.

  25.An automated system of regulation by static shutters imposes

  then a control logic relatively complex and expensive.

  The invention proposes to overcome the drawbacks of the systems which have just been described by proposing a method and a device for automatic regulation of the operating point of a fan, used in an agricultural apparatus the operation of which requires at least one source of pressure different from the atmospheric pressure, between a minimum threshold and a maximum threshold of vacuum upstream (at the inlet) of the fan and a minimum threshold and a maximum threshold of pressure downstream (output) of the fan, which is automatic and

simple realization.

  The invention relates to a method for automatically regulating the operating point of a fan, used in an agricultural apparatus whose operation requires at least one pressure source different from the atmospheric pressure, between a minimum threshold and a threshold maximum pressure downstream of the fan and / or a minimum threshold and a maximum depression threshold upstream of said fan, for a flow rate of air absorbed by the fan included

  between a first and a second terminals.

  According to the invention, the method consists of placing the upstream of the fan in communication with the atmosphere so that the pressure downstream of the fan does not become lower than said minimum pressure threshold and put in communication the downstream of the fan with the atmosphere so that the upstream depression does not

  become not less than the minimum threshold of depression.

  The invention also relates to a device for automatic control of the operating point of a fan, used in an agricultural appliance whose operation requires at least one pressure source different from the atmospheric pressure, between a minimum threshold and a maximum threshold of pressure downstream of the ventilator and / or a minimum threshold and a maximum depression threshold upstream of the ventilator, for a flow rate of air absorbed by the ventilator included

  between a first and a second terminals.

  According to the invention, the device comprises a first valve placed in the upstream part of the fan and a second valve placed in the downstream part of the fan, said first valve being calibrated so as to put the upstream of the fan in communication with the outside. such that the downstream pressure does not become less than the minimum pressure threshold and said second valve is calibrated so as to put the fan downstream in communication with the outside so that the upstream depression does not become

  not below the minimum threshold of depression.

  According to a first embodiment of the invention, said

  first valve is placed in the fan housing.

  According to a second embodiment of the invention, said

  second valve is placed in the exhaust duct of the fan.

  Preferably, said first valve comprises a support placed inside the fan, a shutter applied against its seat by a calibrated spring and whose outer face is in contact with the

atmospheric pressure.

  Preferably, said second valve comprises a support placed outside the fan, a shutter applied against its seat by a tared spring and whose inner face is in contact with the

atmospheric pressure.

  According to a preferred embodiment of the invention, a grid is placed between

  the valve seat and the shutter.

  According to another embodiment of the invention, said first valve is constituted by a prestressed tension spring, with contiguous turns at rest, fixed by at least one turn to the inner face of the fan and at least the last turn of which supports a plate

  closing the central portion of said spring.

  According to another embodiment of the invention, said second valve is constituted by a prestressed tension spring, with contiguous turns at rest, fixed by at least one turn to the outer face of the fan and at least the second turn of which supports a plate

  closing the central portion of said spring.

  According to another embodiment of the invention, at least one of said valves is constituted by a shutter which can close the orifice on which said valve is placed and pressed against its seat by a prestressed torsion spring whose axis is situated in

  a plane parallel to that of the orifice and fixed near the seat.

  The invention further relates to a vacuum seeder comprising at least one vacuum seed distributor and a pneumatic spreader of phytosanitary products, the latter being

  possibly mounted on the drill.

  According to the invention, the drill comprises a single fan and a device for regulating the operating point of said fan according to the invention, at least one distributor being connected upstream of said fan by a vacuum pipe and, possibly, at least a spreader being connected downstream of said fan by a pipe

pressure.

  The invention also relates to a vacuum seeder comprising at least one

  minus a seed-and-depression seed dispenser.

  According to the invention, the drill comprises a single fan and a device for regulating the operating point of said fan according to the invention, at least one distributor being connected upstream of said fan by a vacuum pipe and downstream of said fan.

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  fan by a pressure hose.

  According to a preferred embodiment of the invention, the drill

  additionally comprises at least one pneumatic spreader of phyto-

  sanitary, at least one spreader being connected downstream of said fan by a pressure pipe. The present invention will be better understood and other purposes, advantages and features thereof will become more clearly apparent.

  upon reading the following description of embodiments of

  the invention given in a nonlimiting manner and to which drawings are appended in which: - Figure 1 shows an example of agricultural apparatus on which is mounted the device according to the invention - - Figure 2 shows a sectional view according to II-II of FIG. 1; FIG. 3 represents a sectional view on III-III of FIG. 1; FIG. 4 represents a sectional view along line IV-IV of FIG. 1; and FIG. sectional view of a first example of a valve mounted in the device according to the invention, - Figure 6 shows a sectional view of a second example of a valve mounted in the device according to the invention, - Figure 7 shows a sectional view of a third example of a valve that can be mounted in the device according to the invention and - figure 8 comprises figures 8a and 8b, figure 8a shows a view from above of a fourth embodiment of a valve that can to be mounted in the device according to the invention and the

  Figure 8b shows a sectional view along VIII-VIII of Figure 8a.

  The elements common to the different figures will be designated by

the same references.

  The agricultural apparatus partially shown in the figures,

  has a vacuum seeder and a spreader.

  With reference to FIGS. 1 to 4, the chassis of the agricultural apparatus, not shown, supports a fan 1. This includes

  a housing 2 in which is mounted a rotor 3 secured to an axis 4.

  The axis 4 and the rotor 3 are rotatably mounted in means 5 partially shown in FIG.

  from an engine not shown.

  The casing 2 has a substantially symmetrical shape with respect to the sectional plane II-II passing through the axis 4. In its rear and lower part, the casing comprises at least one manifold.6, defining the inlet (or upstream In this embodiment, the casing 2 comprises a collector 6, connected to a first end of each of two suction ducts 7. The two suction ducts 7 are substantially identical, which is why a single is shown completely in Figure 1. They have a substantially rectangular section and are closed at their second end by a plug 8. On the underside of each suction duct 7 and the housing 2 are formed openings 9. They can be closed by a cap 10 or

  connected to a pipe 11, called depression.

  The casing 2 comprises, in its upper part, a duct 12 which defines the outlet (or downstream) of the fan 1. At the downstream end of the duct 12 are formed openings 13. They may be closed by a plug 10 or connected to a pipe 14 called pressure. In the case where the seed drill mounted on the agricultural machine includes at least one vacuum distributor, as described in patent EP-00 46709 cited above, a vacuum pipe 11 is connected via a cover of suction 15, to one of the two speakers created by the distribution disc 16 inside the housing of the dispenser. The pipe 11 is connected to the enclosure 17 which extends over a portion of the path of the perforations of the disk and which constitutes a vacuum chamber. The other enclosure, contiguous,

serves as a seed tank.

  It is known that the structure of the rotary distribution disk which is provided with a circular file of perforations, is chosen as a function of the average diameter of seeds to be sown and the spacing

  desired seeds in the furrow.

  There are as many distributors as there are rows to be sown. In this

  embodiment, twelve rows can be sown simultaneously.

  If one wishes to sow only a smaller number of grooves, it is then sufficient to close the openings 9 in excess which must be condemned by a plug 10. The other openings 9 will be connected to a disk valve via 'a pipe

  11 and a suction cover 15.

  Downstream of the fan 1, the spreading is possibly carried out for a given row by first connecting a pressure hose 14 in one of the openings 13 formed in the outlet duct 12 of the fan. The free end of the pipe 14 is then connected to

  the inlet of a venturi 18. Figure 4 shows, in section according to IV-

  IV, an example of a three-row venturi. The pipe 14 may be connected to a single row venturi and preferably to a three, six or nine row venturi. "Rank" denotes an outlet 19 of the venturi. The phyto-sanitary products, which must be projected by the spreader, are introduced into the venturi 18 via a chute 20 which is connected to a hopper, not shown on

Figure 1.

  If a single-row venturi is used, the pipe 14 allows the spreading of a single phytosanitary product, on a single

single furrow.

  When a three-row venturi is used, the pipe 14 makes it possible, for example, to spread a phyto-sanitary product over three grooves or to spray three phytosanitary products.

different on a single furrow.

  Similarly, if a six-row venturi 19 is used, the pipe 14

  allows, for example, the spreading of a single phyto-

  six furrows or the application of three plant products.

sanitary in two rows.

  It may be interesting to spread different plant protection products on a furrow, during the same passage of the agricultural machine. For the same furrow, an outlet 19 of a venturi 18 can make it possible to transport fertilizers in the open furrow at the moment when the seed is released into the furrow, another outlet 19 of the venturi transporting herbicides to the furrow after closure. this one and a last exit of the venturi then sending

  insecticides on the same furrow closed.

  In this embodiment, the openings 13 formed in the outlet duct 12 of the fan are twelve in number; six

  openings being provided on two opposite faces of the duct 12.

  On the casing 2 of the fan 1 is mounted a first valve 21.

  In this exemplary embodiment, the valve 21 is mounted so that its axis 22 is in the extension of the axis 4 of the rotor 3 of the fan 1. With reference to FIG. 5, the valve comprises a support 23 which is fixed to the housing 2 by means of spacers 24, screws 25 and nuts-26. The valve 21 further comprises a

  shutter 27, having substantially the shape of a disc.

  The shutter 27 comprises, substantially at its center, a recess 28 in which is placed a screw 29 which has at one end a head 29a and which is fixed at its other end to the support 23 of the

  valve, via a nut 30a and a lock nut 30b.

  The shutter 27 can bear on the housing 2 of the fan at its periphery, this portion of the housing 2 forming the seat 32 of the valve. Finally, a helical spring 31 is placed between the inner face of the support 23 and the inner face of the shutter 27, being wound around the screw 29. The screw 29 serves as a guide for the shutter 27 and the spring 31 The spring 31 makes it possible to apply the shutter 27 against its seat 32. As will be seen later, the spring 31 of the valve 21 is tared to a determined value. Preferably, a grid 33 is placed between the seat 32 of the valve and its shutter 27. The advantage of this grid 33 will be

specified below.

  It is understood that the outer face of the shutter 27 or the outer face of the grid 33 when provided, is in contact with the atmospheric pressure outside the housing 2, while the body of the valve 21 is placed inside the casing 2 of the fan in which there is a pressure lower than the atmospheric pressure

when the fan is running.

  There is also a second valve 34 in the outlet duct 12 of the fan 1. The valve 34 is shown in detail with reference to FIG. 6. The valve 34 has slight differences with the valve 21. -In particular, for reasons in particular, the support 23 of the valve 31 has substantially the shape of a bell while the support 35 of the valve 34 is substantially planar. The support 35 is fixed to the housing 2 by means of tubular spacers 36, screws 37 and nuts 38. The valve comprises a shutter 39 whose shape is substantially that of a

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  disk. The shutter is guided by a screw 29, fixed by the end of its rod to the support 35 by a nut 30. A spring 40 is arranged similarly to the spring 31, it is likewise calibrated to a determined value. The spring 40 allows to apply the shutter 39 against the seat 41 of the valve. Preferably, a grid 33 is placed between the

valve seat and shutter.

  It is understood that the outer face of the shutter 39 or the outer face of the grid 33 if it is provided, is in contact with the pressure greater than the atmospheric pressure prevailing inside the outlet duct 12 of the fan 1 when it works, while the body of the valve 34 is placed outside

  duct 12, which is at atmospheric pressure.

  It is also possible to replace the first and / or second valve (s) by a third valve 42 as shown in Figure 7. This valve is constituted by a helical spring 43, at least the first turn 44 is fixed to the periphery of the orifice formed in the casing 2 and of which at least the last turn 46 is fixed to a plate 47 whose shape is substantially identical to the

  section of the spring 43, so as to close the central portion of the

  this. The spring 43 is a tension spring prestressed to a value

  determined, so that it is at contiguous turns at rest.

  Preferably, as indicated in FIG. 7, an intermediate piece 48 is fixed at the periphery of the orifice 45 formed in the casing 2. This piece 48 comprises a portion 49 of substantially cylindrical shape and of section that is smaller than that of the spring, so that the first turns of the spring surround the portion 49 and can be attached thereto. Similarly, the plate 47 preferably comprises a portion 50 of substantially cylindrical shape and of lower section than the spring, so that the last turns of the spring 43 surround the portion 50

  and can be attached to it.

  When this third valve 42 replaces the first valve 21, the inner face of the plate 47 is in contact with the atmospheric pressure, while it is in contact with a pressure greater than the atmospheric pressure when the third valve 42

replaces the second valve 34.

  It is also possible to replace the first and / or

- ii -

  second valve (s) by a fourth valve 51 as shown in Figures 8a and 8b. This valve comprises a shutter 52 substantially flat and whose shape is chosen substantially identical to that of the orifice 53 formed in the housing 2 so as to close it. A torsion spring 54 is fixed by its two free ends 55 to the face 56 of the shutter 52, opposite to that facing the orifice 53. The spring 54 is wound around an axis 57, placed in a plane parallel to that of the orifice 53 and fixed to the housing at the seat 58. Its central portion 59 is applied against the housing. It is prestressed so that the shutter 52 is at rest applied against its seat 58 and rises at a given pressure, thereby

  in communication the inside of the housing 2-with the outside.

  When this fourth valve 51 replaces the first valve 21, the face of the shutter 52, facing the orifice 53, is in contact with the atmospheric pressure, while it is in contact with a pressure greater than atmospheric pressure. when the fourth

  valve 51 replaces second valve 34.

  We will now describe the operation of the device according to the invention, mounted on an agricultural machine as described above, the seeder comprises at least one vacuum distributor whose enclosure constituting the vacuum chamber is connected to a suction duct 7 via a vacuum pipe 11, and whose spreader comprises at least one venturi, connected to the outlet duct 12 of the fan via a pipe 14 of pressure when the spreader is in function , while the corresponding opening or openings 13 are closed off by plugs 10

  when the spreader is not used.

  For an air flow rate between a first and a second terminal and for any number of pressure pipe (s) 14 and vacuum pipe (x) 11 connected to the fan, the good operation of the spreader requires that the pressure downstream of the fan 1, that is to say in the outlet duct 12, is always greater than or equal to a first minimum threshold or minimum pressure threshold. In the same conditions, the smooth running

  of the seeder imposes that the depression upstream of the fan 1, that is to say

  say in suction ducts 7, either always (in absolute value) greater than or equal to a second minimum threshold, or minimum threshold of -12-

- 12 - -2642480

  depression, even if no pressure pipe 14 is connected to the fan. The setting of the spring 31 of the first valve 21 is chosen so that the shutter 27 is lifted from its seat 32 (as shown in the lower part of Figure 5), when the vacuum inside the housing 2 of the fan becomes superior (in absolute value) to a first value. The opening of the valve corresponding to this first value makes it possible to limit the vacuum at the inlet of the fan to a first maximum threshold or maximum threshold of depression, by admission of air at atmospheric pressure upstream of the fan. As indicated above, the characteristics of a fan are such that for a flow of air absorbed by the fan, the total pressure of the fan is imposed. The first maximum threshold or the corresponding calibration of the spring 31 is chosen so that the outlet pressure of the corresponding fan is equal to the first minimum threshold. Thus, the pressure downstream of the

  fan 1 will always be higher than the first minimum threshold.

  Likewise, the setting of the spring 40 of the second valve 34 is chosen so that the shutter 39 moves away from its seat 41 (as illustrated in the lower part of FIG. 6) when the pressure

  inside the casing 2 becomes greater than a second value.

  The opening of the valve then makes it possible to limit the increase in the pressure at the fan outlet to a second maximum threshold or maximum pressure threshold, by exhausting compressed air towards the atmosphere. This second maximum threshold (or the corresponding setting of the spring 40) is chosen so that the vacuum at the fan inlet is equal to the second minimum threshold. Thus, the depression upstream of the fan 1 is always higher (in absolute value)

at the second minimum threshold.

  It is then understood that it is sufficient to choose appropriately the setting of the springs 31 and 40 of the first and second valves 21 and 34 so that the operation of the fan 1 is regulated between the minimum threshold and the maximum threshold of depression and between the threshold minimum and

the maximum pressure threshold.

  The tests carried out have shown that the operation of the first and second valves 21 and 34 can cause vibration problems. Indeed, the movement of the shutter 27, 39, relative

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  at its seat 32, 41 causes all or nothing operation of the valve 21, 34. Therefore, is preferably placed between the seat of the valve 32, 41 and the shutter 27, 39 a grid 33 which allows orienting the air flows more favorably and creating a film of air between the grid 33 and the shutter 27, 39 in order to damp the

  shocks between the shutter 27, 39 and its seat 32, 41.

  It is found that the third valve, described with reference to Figure 7, avoids the disadvantages of valves-operating all or nothing. Indeed, the opening of the valve is effected by a gradual detachment of the turns relative to each other, the air escaping through the spaces thus formed between the turns. This

  third valve makes unnecessary the presence of a grid 33.

  It is noted that it is the same for the fourth valve described

with reference to Figure 8.

  The device according to the invention has been described in relation to an agricultural implement whose seed drill comprises at least one distributor of

  vacuum seeds and whose spreader is pneumatic.

  It is likewise possible to mount the device according to the invention on an agricultural implement whose seed drill comprises at least one seed distributor operating at the same time thanks to a source of pressure and a source of depression. In this case, at least one distributor is connected to the fan via a pressure hose and

of a vacuum pipe.

  In this case, the farm implement may also include a spreader

phytosanitary products.

  Tests have been carried out for a fan whose characteristics are the following: - for an air flow absorbed by the fan of between 0.14 and 0.36 m3 / s, the total pressure of the fan is 12000 Pa, - - for an air flow rate between 0.36 and 0.56 m3 / s, the total pressure of the fan decreases continuously to 10500 Pa, - for an air flow rate between 0.56 and 0.69 m '/ s, the total pressure of the fan decreases continuously until

9500 Pa.

  Proper calibration of the valves of the device according to the invention makes it possible to obtain a pressure downstream of the fan between

- 14 -

  5400 Pa and 7300 Pa and a depression upstream of between 2200 Pa and 4700 Pa for a flow of air absorbed by the fan included

between 0.14 and 0.69 m3 / s.

  Finally, the reference signs inserted after the

  technical features set out in the claims, have as their

  purpose only to facilitate the understanding of the latter and may not in any circumstances have the effect of limiting the invention to

  particular embodiments that have just been described.

- 15 -

Claims (13)

  1. A method for automatically controlling the operating point of a fan, used in an agricultural appliance whose operation requires at least one source of pressure different from the atmospheric pressure, between a minimum threshold and a maximum pressure threshold downstream of the fan and / or a minimum threshold and a maximum threshold of depression upstream of said fan, for a flow rate of air absorbed by the fan between a first and a second terminal, characterized in that it consists in putting in communication the upstream of the ventilator with the atmosphere so that the pressure downstream of the ventilator does not become lower than said minimum pressure threshold and put in communication the downstream of the ventilator with the atmosphere so that the upstream depression does not   become not less than the minimum threshold of depression.   2. Device for the automatic control of the operating point of a ventilator, used in an agricultural appliance the operation of which requires at least one source of pressure different from the atmospheric pressure, between a minimum threshold and a maximum pressure threshold downstream of the fan and / or a minimum threshold and a maximum depression threshold upstream of the fan, for a flow of air absorbed by the fan between a first and a second terminal, characterized in that it comprises a first valve (21). placed in the upstream part of the fan and a second valve (34) placed in the downstream part of the fan, said first valve being calibrated so as to put the upstream of the fan in communication with the outside so that the downstream pressure does not become lower than the minimum pressure threshold and said second valve is calibrated so as to put the fan downstream in communication with the outside of such the kind that depression into   upstream does not become less than the minimum threshold of depression.   3. Device according to claim 2, characterized in that said first valve (21) is placed in the housing (2) of'ventilateur (1).   4. Device according to one of claims 2 and 3, characterized   in that said second valve (34) is placed in the conduit of outlet (12) of the fan (1). - 16 - 2642480   5. Device according to one of claims 2 to 4, characterized   in that said first valve (21) comprises a support (23) placed inside the fan (1), a shutter (27) pressed against its seat (32) by a calibrated spring (31) and whose external face is in contact with the atmospheric pressure.   6. Device according to one of claims 2 to 5, characterized   in that said second valve (34) comprises a support (35) placed outside the fan (1), a shutter (39) pressed against its seat (41) by a tared spring (40) and whose internal face is   contact with atmospheric pressure.   7. Device according to one of claims 5 or 6, characterized   in that a grid (33) is placed between the seat (32, 41) of the valve (21, 34) and the shutter (27, 39).   8. Device according to one of claims 2 to 4, characterized   in that said first valve (21) is constituted by a prestressed tension spring (43) with turns contiguous at rest, fixed by at least one turn (44) to the internal face of the fan (1) and at least the last of which spire (46) supports a plate (47)   closing the central portion of said spring.   9. Device according to one of claims 2 to 4 and 8,   characterized in that said second valve (34) is constituted by a prestressed tension spring (43) with contiguous turns at rest, fixed by at least one turn (44) to the external face of the fan (1) and at least the second turn (46) supports a plate (47)   closing the central portion of said spring.   10. Device according to one of claims 2 to 4, characterized   in that at least one of said first and second valves (21,34) is constituted by a shutter (52) which can close off the orifice (53) on which said valve is placed, by being pressed against the seat (58) of the valve by a prestressed torsion spring (54) whose axis (57) is situated in a plane parallel to that of the orifice (53) and fixed to proximity of said seat (58).   11. Vacuum seeder comprising at least one vacuum seed distributor and, optionally, at least one pneumatic spreader for phytosanitary products, characterized in that it comprises a single fan and a regulating device of said   fan according to one of claims 2 to 10, at least one - 17 - 2642480   distributor being connected upstream of said fan by a pipe (11) of depression and at least one spreader being connected to the downstream of said   fan by a pipe (14) pressure.   12. Vacuum seeder with at least one seed distributor pressure and vacuum, characterized in that it comprises a single fan and a control device of said fan   according to one of claims 2 to 10, at least one distributor being   connected upstream of said fan by a pipe (11) of depression and   downstream of said fan by a pipe (14) pressure.   13. Vacuum seeder according to claim 12, characterized in that it further comprises at least one pneumatic spreader of plant protection products, at least one spreader being connected to the downstream of said   fan by a pipe (14) pressure.